How to pull sequencer data from the top left corner and to the right lower corner
Python's sorted() can use a custom function that defines the key to use when sorting a list and it also has a reverse option.

def start(strip):
    return strip.frame_start

def end(strip):
    return strip.frame_start + strip.frame_final_duration


Then you can sort by start or end frame with

seq_strips = bpy.context.scene.sequence_editor.sequences

strips_by_start = sorted(seq_strips, key=start)

strips_reversed = sorted(seq_strips, key=end, reverse=True)